1. Field of the Invention
The present invention relates to a personal ornament (accessories) having a white coating film, and a process for producing the personal ornament. More specifically, the present invention relates to a personal ornament having a hard white stainless-steel-colored coating film, and a process for producing the personal ornament; and relates also to a personal ornament having a hard white platinum-colored or platinum-alloy-colored coating film, and a process for producing the personal ornament. (Hereinafter the “personal ornament” is simply referred to as an “ornament”.)
2. Description of Related Art
Heretofore, many ornaments such as watches, necklaces, pendants, and brooches are made from a copper alloy owing to workability, material cost, and other reasons.
However, a personal ornament made from a copper alloy, which is less corrosion-resistant as the base material, is usually covered with a plating film formed by wet plating to protect the base material from corrosion. This plating film is usually constituted of an underlying nickel plating film formed by wet plating and an outermost plating film formed thereon by wet plating. For coloring the outermost layer golden, a gold plating film is formed on the nickel plating film surface by wet plating. For coloring the outermost layer white, a palladium plating film, a palladium alloy plating film, or a rhodium plating film is formed on the nickel plating film by wet plating. The plating film is generally formed in a thickness in the range of 1-5 μm.
The aforementioned ornaments, however, have the disadvantage of high cost owing to the noble metal-containing outermost plating film for corrosion resistance. Therefore, low-priced personal ornaments naturally have a thin outermost plating film, lacking in long-term corrosion resistance. Moreover, in the production of the low-priced ornaments, the noble metal plating bath should be strictly controlled and maintained in order to obtain steadily a thin outermost plating film, and the workers for the plating operation should have high skill in order to obtain steadily the outermost plating film of the desired color tone. Furthermore, an inexpensive personal ornament having a characteristic white color of the stainless steel, or an inexpensive personal ornament having a characteristic beautiful white color of a platinum or platinum alloy has not yet been produced at a low cost.
Therefore, the inventors of the present invention disclosed, in JP-A-3-120355 (The term “JP-A” herein means “an unexamined Japanese Patent Publication”), a white ornament comprising a base material coated on the surface with a white hard film and further coated thereon with a platinum or platinum alloy coating film. However, the ornament does not have the characteristic white color demanded in the market although it gives high-quality image. An ornament having a white coating and a process for producing the ornament are disclosed in the specification in international laid-open publication of WO-02/00958 of international patent application (PCT/JP01/05130) based on priority by Japanese Patent Application No. 2000-192077 (filed on Jun. 27, 2000), not a prior art. This ornament is constituted of a less corrosion-resistant low-quality metal (including an alloy) as the base and having its surface covered with a white-colored stainless steel coating film for long-term corrosion-resistance, and is low-priced.
The disclosed ornament has a metal base article which is covered with a white-colored stainless-steel film formed by dry plating. The ornament, which is constituted of a low-quality base metal like a copper alloy, is coated with a wet-plated nickel film or a dry-plated film of titanium carbide, zirconium carbide, or the like as an underlying layer and further coated with a stainless steel film as the surface layer.
However, such an ornament, which has an outermost layer coated only with a white stainless-steel film without a noble metal surface coating, is lacking in massiveness image and high-quality image of the surface. Moreover, this white coating film has a disadvantage of low hardness and low scratch resistance due to the base material or underlying plating film, tending to deteriorate in the external appearance quality in a short period. Furthermore, in a case where a nickel plating film or nickel-alloy plating film is formed as the underlying plating film depending on the kind of the base material, nickel allergy can be produced to cause skin rash or eczema with individual difference.
Accordingly, an ornament is demanded which has high-quality image like stainless steel coating film, not deteriorating readily in the external appearance by scratching or other causes, and does not cause metal allergy. The process for producing such an ornament is also demanded.
In the aforementioned JP-A-3-120355, a TiN coating film is formed as the white hard film in the Example. The coating film is dark grey or light gold in color. Therefore, a platinum coating film or a platinum alloy coating film formed on the TiN coating film is affected by the color tone of the white hard coating film (TiN coating film), not developing a characteristic beautiful color of platinum or a platinum alloy. Further, in the case where the TiN coating film is thin, an impact or a pressure from the outside can dent the base metal, denting also the platinum or platinum-alloy coating film to form a defect, disadvantageously. The article in the above Example has a platinum coating film of 0.1 μm thick, which is disadvantageous in cost. Furthermore, if the formation of the platinum or platinum alloy coating film is not successful, the platinum or platinum alloy coating film is removed and newly formed again. This film removal is conducted by use of aqua regia. The aqua regia will corrode not only the white hard TiN coating film but also the metal base surface, which makes impossible the film reformation, disadvantageously.
Therefore, an ornament is demanded which has a characteristic color of platinum or a platinum alloy coating film, and superior quality, not deteriorating readily in the external appearance by denting, scratching or other causes, and having a white coating film of high quality with a lower cost. Also a process for producing the ornament is also demanded which enables removal of the platinum or platinum alloy coating film without corrosion of the ornament base, the underlying layer or the titanium carbide layer, and enables regeneration of the ornament by reforming the platinum or platinum alloy coating layer.
The present invention solves the above problems by providing a personal ornament which gives superior quality, does not readily deteriorate in the external appearance by scratching or other causes, and has a white coating film having high-quality image like a stainless steel film, especially does not cause metal allergy, and also provides a process for producing such an ornament.
Further, the present invention provides a personal ornament which gives a characteristic color of platinum or a platinum alloy, superior quality, does not readily deteriorate in the external appearance by scratching or other causes, has a white coating film of high quality at a lower cost, and provides a process for producing the ornament. Still further, the present invention provides a personal ornament which enables removal of the defective platinum or platinum alloy coating film without corrosion of the ornament article base, the underlayer or the titanium carbide layer to regenerate the ornament by reforming the platinum or platinum alloy coating film, and provides a process for producing the same.